// map对象
function Map() {  
 var struct = function(key, value) {  
  this.key = key;  
  this.value = value;  
 }  
   
 var put = function(key, value){  
  for (var i = 0; i < this.arr.length; i++) {  
   if ( this.arr[i].key === key ) {  
    this.arr[i].value = value;  
    return;  
   }  
  }  
   this.arr[this.arr.length] = new struct(key, value);  
 }  
   
 var get = function(key) {  
  for (var i = 0; i < this.arr.length; i++) {  
   if ( this.arr[i].key === key ) {  
     return this.arr[i].value;  
   }  
  }  
  return null;  
 }  
   
 var remove = function(key) {  
  var v;  
  for (var i = 0; i < this.arr.length; i++) {  
   v = this.arr.pop();  
   if ( v.key === key ) {  
    continue;  
   }  
   this.arr.unshift(v);  
  }  
 }  
   
 var size = function() {  
  return this.arr.length;  
 }  
   
 var isEmpty = function() {  
  return this.arr.length <= 0;  
 }   
 this.arr = new Array();  
 this.get = get;  
 this.put = put;  
 this.remove = remove;  
 this.size = size;  
 this.isEmpty = isEmpty;  
} 